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Mission Status 2011

Tim Larson, Stardust-NExT Project Manager

February 1, 2011
Just over two weeks before its flyby of comet Tempel 1, NASA's Stardust spacecraft fired its thrusters to help refine its flight path toward the comet. The Stardust-NExT mission will fly past comet Tempel 1 on Valentine's Day (Feb. 14, 2011).

The trajectory correction maneuver, which adjusts the spacecraft's flight path, began at about 4 p.m. EST (1:00 p.m. PST) on Monday, Jan. 31. The Stardust spacecraft's rockets fired for 130 seconds, consumed about 300 grams (10.6 ounces) of fuel and changed the spacecraft's speed by 2.6 meters per second (about 5.8 mph).

"An almost six-miles-per-hour change may seem insignificant when we're closing in on the comet at 24,236 miles per hour [39,000 kilometers per hour]," said Tim Larson, Stardust-NExT project manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "But we're still two weeks and 8.37 million miles [13.5 million kilometers] away from the comet. At that distance, our burn will move our location at time of closest approach to the comet by almost 1,900 miles [3,058 kilometers]. By observing the results of these planned maneuvers and making further rocket burns, that's how we get a spacecraft to be where we want it, when it's on the other side of the solar system."

NASA's plan for the Stardust-NExT mission is to fly the spacecraft to target a point in space about 200 kilometers (124 miles) from comet Tempel 1 at the time of its closest approach at about 8:56 p.m. PST on Feb. 14 (11:56 p.m. EST). This is a bonus mission for the comet chaser, which previously flew past comet Wild 2 and returned particles from its coma to Earth. During this bonus encounter, the spacecraft will take images of the comet's surface to observe what changes have occurred since a NASA spacecraft last visited. (NASA's Deep Impact executed an encounter with Tempel 1 in July 2005).

Along with the high-resolution images of the comet's surface, Stardust-NExT will also measure the composition, size distribution and flux of dust emitted into the coma, and provide important new information on how Jupiter-family comets evolve and how they formed 4.6 billion years ago. A Jupiter-family comet is a comet whose orbit has been modified by close passages to Jupiter. They have orbital periods less than 20 years.

Launched on Feb. 7, 1999, Stardust became the first spacecraft in history to collect samples from a comet (Wild 2), and return them to Earth for study. While its sample return capsule parachuted to Earth in January 2006, mission controllers were placing the still-viable spacecraft on a path that would allow NASA the opportunity to re-use the already-proven flight system if a target of opportunity presented itself. In January 2007, NASA re-christened the mission "Stardust-NExT" (New Exploration of Tempel), and the Stardust team began a four-and-a-half year journey for the spacecraft to comet Tempel 1. This will be the second exploration of Tempel 1 by a spacecraft (Deep Impact).

Stardust-NExT is a low-cost mission that will expand the investigation of comet Tempel 1 initiated by NASA's Deep Impact spacecraft. JPL, a division of the California Institute of Technology in Pasadena, manages Stardust-NExT for the NASA Science Mission Directorate, Washington, D.C. Joe Veverka of Cornell University, Ithaca, N.Y., is the mission's principal investigator. Lockheed Martin Space Systems, Denver, built the spacecraft and manages day-to-day mission operations.

January 19, 2011
The spacecraft continues to operate as expected and all subsystems are healthy on approach to comet Tempel 1. This week the spacecraft started to tip back and forth to the imaging attitude in order to fix the Navcam mirror in a position that results in less scattered light reaching the CCD. This strategy has resulted in much lower background noise. The comet has not yet been detected in the images, and may not be detected for another week yet. The team continues to prepare for the Tempel 1 flyby by completing the tests of the encounter sequences.

January 6, 2011
The spacecraft is healthy, and began the new year with a cold boot to clear a MEEB (memory address latch-up) that had occurred late in 2010. This cold boot clears the latched line and resets the memory to its factory settings. The activity, performed on January 4 went exactly as expected, and the spacecraft is now back in its comet approach configuration, ready to take the next set of Optical Navigation images on January 6. The mission plan has changed substantially over the last few weeks in response to two key challenges: a new, lower, estimate of remaining fuel, and not detecting the comet in the OpNav images. Current estimates show that the comet may not be bright enough to detect with the Navcam until the latter half of January. Since optical navigation is key to the approach targeting, the trajectory correction maneuver plan has changed to accommodate this information. The approach maneuvers are now planned as follows: TCM 31 on January 31, TCM 32 on February 7, and TCM 33 as previously planned on February 12 (E-48 hours). The approach science imaging has now been postponed until E-7 days, with only OpNav imaging occurring between now and February 7. This new plan accommodates provides positive fuel margin through encounter, preserves fuel reserves to accommodate larger than expected deviations in the comet ephemeris estimates, and places the TCMs at times best able to accommodate late detection of the comet. The spacecraft team is completing the tests of the approach and flyby sequences, and is building the approach sequences that will control the spacecraft over the next several weeks. The JPL Center Management Council briefing is scheduled for Friday, January 7, and the NASA Headquarters Division Program Management Council briefing is scheduled for January 20.

January 2, 2011

All subsystems are nominal. Daily contacts continue, including use of 70m antennas for improved downlink rates. Two sets of images of Tempel-1 have been collected, and the team is analyzing the images in order to update our prediction of the comet's trajectory. The next imaging opportunity will be late tomorrow night. Stardust's encounter is in 54 days. Tempel-1 is now less than 31,200,000 miles away.

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